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(Located in the USA) I've inherited a 220V (or 240V?) circuit which is just capped off inside a junction box. It's hooked up to a 30A breaker, and seems fine, except that it's only a 3-wire run--no ground. I'd like to make it usable for running some 220V computer equipment, but I need a ground to do so.

I'm about 10' from the breaker box, inside a washer/dryer closet, but the wire was pulled through the walls. Should I run conduit with a ground wire in it from the nearby breaker box and pull it into the junction box with the other three wires? Suggestions?

I just want to do this correctly, and safely the first time!

Well, now it appears I remembered incorrectly...there are only TWO wires! What were they thinking when they did this? More importantly, what should I do to safely fix this for me and anyone who might later open this up to work on it?

insane 2-wire 220v thing

Luke G.
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  • These may answer your question about a "retrofit ground" (https://diy.stackexchange.com/questions/99429/house-wiring-and-grounding-how-do-you-retrofit-an-old-house-and-ground-it) and (https://diy.stackexchange.com/questions/36350/how-do-i-add-grounding-to-my-old-electrical-wiring) – Hari Apr 12 '18 at 21:31
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    Possible duplicate of How do I add grounding to my old electrical wiring? – Daniel Griscom Apr 12 '18 at 21:35
  • beware old answers. The rules were greatly liberalized in 2016 (NEC 2014) . – Harper - Reinstate Monica Apr 12 '18 at 22:23
  • What wiring method was used for the homerun of this circuit? Are you OK with having only 240V at this location? – ThreePhaseEel Apr 12 '18 at 22:37
  • @ThreePhaseEel, yes, I've got lots of open breaker slots, so I'm fine with only having 220V here. – Luke G. Apr 12 '18 at 23:59
  • Can you tell us what wiring method was used here? Was the existing circuit wired using a plastic-sheathed cable, some sort of metal-armored cable, or wires in some sort of conduit? – ThreePhaseEel Apr 13 '18 at 00:12
  • Well, this may be more complicated than I thought...I guess I remembered the number of wires incorrectly...there are only TWO! What did this person do?? (Adding photo to initial post if possible) – Luke G. Apr 13 '18 at 01:01
  • How much power does said 220V computer equipment pull? – ThreePhaseEel Apr 13 '18 at 01:11
  • Maximum I'd ever plan to pull here would be somewhere between 6 to 8 amps. – Luke G. Apr 13 '18 at 01:14
  • Can you make this computer equipment run on 120V instead? – ThreePhaseEel Apr 13 '18 at 02:13
  • @ThreePhaseEel, yes, I could run it on 120V (the power supply says both 100-140VAC input and 200-240VAC input). Since I had the unused '220V', and since I think I read that the power usage is more efficient on 220V, I just thought I could utilize this as a 220V circuit. – Luke G. Apr 13 '18 at 11:04
  • FWIW, I was going to use a NEMA 6-30R here, which only specifies black, white, and ground...is that still safe here without a neutral? – Luke G. Apr 13 '18 at 11:58
  • Can you figure out what wiring method is running to that box? It looks like armored cable, but I can't tell for sure – ThreePhaseEel Apr 13 '18 at 22:14
  • Well, nevermind...I just uncapped the wires to verify which breaker they went with and they are totally dead. :/ Thanks for helping me troubleshoot this, but it looks like if I want a 240V receptacle here I'm going to be doing a homerun anyway. – Luke G. Apr 14 '18 at 21:42

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